Means and method of drilling with aerated drilling liquids



April 7, 1959 R. A. BOBO MEANS AND METHOD OF DRILLING WITH AERATED DRILLING LIQUIDS Fi led July '7, 1955 IN VEN TOR.

4 TTOR/VEVS United States Patent() ice MEANS AND METHOD OF DRILLING WITH AERATED DRILLING LIQUIDS Roy A. Bobo, Houston, Tex., assignor to lhillips Petroleum Company, a corporation of Delaware Application July 7, 195 5, Serial No. 520,485

8 Claims. c1. ass-1.8

This invention relates to an improved rotary well drilling process and apparatus.

Of all its problems, the oil industryshould be most acutely aware of the benefits to be derived from reducing drilling costs. Since the expenditure for drilling wells amounts to a sizable portion of each companys budget, improvements in drilling methods or drilling technique will result in substantial savings. i

It has been found that using-"a light weight drilling fluid often increases the drilling rate and reduces'the numher of bits used, thus decreasing drilling costs. In some instances air or natural gas have been used as the-circulating fluid but an air-lightened-liquid-circulating fluid has the following advantages over air or gas alone:

(1) Low pressure water zones can be penetrated. With air or gas alone, presence of moisture balls up the cuttings, causing bridging and locking of the pipe in the hole.

(2) Safer operations result since quick weight buildup can be obtained when needed by shutting ofi the air and circulating with mud;

(3) The mud phase makes it much easier to obtaina gas tight seal at the drilling head. v

(4) The sleeve bearing effect of the liquid phase between the drill collars and the walls of the hole reduce the tendency toward crooked holes. p

(5 Cuttings for sample purposes are larger and easier to catch since they remain with the liquid phase;

(6) The hole, being continually subjected and conditioned to mud, will standup better. When air or gas has been used, sloughing often occurs when the hole is filled with mud. Sloughing also is likely with air drilling when small quantities of water are encountered. I

Aerated mud has the ,following advantages over normal drilling methods:

(l) Faster drilling rates and increased bit life result.

(2) Good tests. are obtained on all productive zones that are penetrated without resorting to expensive drill stem tests. I

(3) Less horsepower is required for drilling.

. (4) Wear, and tear on equipment is considerably reduced.

,The introduction of both air and mud into the drilling string requires separate equipment for each phase. That for the mud phase remains identical to that employed in conventional mud drilling. The air phase, in runs made thus far, wasdeliveredv by a conventional air comundesirable. 1

I ffif f i tional threading and coupling means. As the upper end 'of the drillstringisopened to the atmosphere the pres- 'sure in the aerated mud due to the compression of the air therein is expanded upwardly and overflows or unloads onto the floor of the drilling-rig, whichis obviously Another problem arisesiin connectionwith theme. of

aerated drilling mud. in rotary drillingywhen it'is, desirable to change froni anqn aerateddrilling mud to an aerated drilling mud which is of considerably less density and of lower viscosity .than the IIOHrfiCl'3t6d-Il1lld. Rotary drilling bits areprovided with. conduits .or passageways whichpermit flow-of drilling fluid from the hollow drill string .intofthe. bore hole outside the bit and theseconduits are....conventionallyj adjusted in transverse cross sectional. area so. asto provide. a suitable pressure drop across thedrill bit forconventional drilling mud. When the change is made in-the drilling process to an aerated drilling mud which has considerably lower density and viscosity, the pressure 'drop across the bit is greatly decreased and it is 'desirableto'reducethe capacity of the flow' passageway thru the bit without removing the bit a method and means for rotarywell drilling utilizing an aerated drilling fluid such'as an aerated drilling "mud. Another object is to provide a method. and means for preventing or minimizing ;ov.erflo'w or self-unloading of an earated drilling fluid'from the upper end of the drill" string when adding joints to the string. It is also pressor connected to the standpipe thru the equipment illustrated and described herein.v

One of the problems which arises when utilizing an aerated drilling liquid, such as an aerated drilling mud;

in rotary drilling is the self unloading of the aerated liquid from the drill string when the upper end of the drill string is opened to add joints of pipe to the drill string. This step entails disconnecting the kelly from the upper end of the drill string as hole is made and attaching an object of the invention toprovidea' method of changing thepi'ess'ure drop acrosslthe drillbit when. changing from a non-aerated drilling'fluid to an aerated,"less dense and less viscous fluid without pulling the bit. 5 Other objects of the invention .willrbecome apparent from 'a consideration of the accompanying disclosure.

1 have found that the incorporation of a check valve in the drill string just below the kelly permits the downward flow of the aerated drilling mudtherethru and prevents upflow therethru when theupper end of the di'illstring' is opened to the atmosphere. IAsh'ole is made andadditional pipe joints are attached to the upper end of the drill string, the check valve progressively moves down the 'hole and is relocated or repositioned closer to the kelly when the string is pulled for any reason, such as for the replacement of th'e bit. In operation where the earth formation being penetrated is such that a drill bit is worn out very slowly'and quite a number of joints are added to the string before pulling the'bit, it is desirable to run another upwardly closing check valve several joints after running the first'check valve so as to prevent unloading of some of the drilling fluid due to expansion of the gas in the hollow drill string between the first run check valve and the upper end of the string. g

In some'd'rilling operations; it 'is' desirable to drillt o a given; depth utilizingflonvgntiorral drilling-mud and then to shift to an aerated drilling fluid of considerably less density and viscosity. This istrue, for example, when aerated mud is used to prevent lost circulation in a portion of the hole. Also, it is necessary to displace the aerated mud with non-aerated mud each time a new hit is run to provide the desired higher pressure obtained with nonaerated mud. I havefound that it is feasible to insert a small body of relatively high density, such as a metal,

' plastic, or rubber ball, into the drilling mudat the upper or adding another joint of pipe to the string by con'venend of the drill string when the same-is open so that as thedrilling mud is circulated thru the drill; string the ball arrives at the drill bit: and seats in one of the'conduits passing thru the'drill bit thereby shutting off flow thruthis conduit and increasing the pressure .drop across .the drill bit. This change in flow capacity renders the drill bit more suitable for drilling with the less dense aerated drilling -mud.

Theterm *aerated drilling fluid is tozbeunderstood to :mean a drilling fluid whichlcontains .air or other gas in 'compressedcondition so as to render ;the fluid substantially "less dense. Theterm -includes all of .etheconventional drilling fluids, such as oil, water, mud, :etc., which L-have been aerated. However, :the userof aerateddrilling mud is preferred-even though the invention :is broadly applicable to aerated drilling tfiuidsof great variation in density.

A more complete understanding of the invention may :be hadfrom a consideration ofY-the drawing of which .Figure -1 is a. schematic elevationalwiew, partly in section, showing "a rotary drill :string *in an r earth formation {and an arrangement of :equipment for rotary .drilling with an aerated drilling fiuidyandrFigure 2 is a longitudinal cross section of a conventional rotary drill :bitof the roller bearing rock-bit two-cone type.

Referring to Figure 1, :the equipment shown is associated with .a well'bore -'int o which is cemented a casing 12. .Adrill :string :14 .comprising a series of pipe joints is connected by'threaded couplingsin conventional manner. A bit 16' is threadedonto the lower endof the drill string. vAttachedto-thecasing above'the earth level .18 is adrilling head 20 which may be of any suitable type, such as a conventionalShafEer drillinghead. =Drill :string '14 formsran annularespace-22wwith thecasing and .the borehole below the' casing. This annular space is scaledoiftat the upperend by. drilling head20 which 1 also forms-arotary seal withxakelly zdsorassto prevent overf-flOW Of .-mud rat the upper -end ther eof. except -.thru outlet conduit 26 which connects :Wlthyfi .section. of the. casing -su-bjacent the drilling ahead.

Kelly 24 extends upwardly-zthru floor "28 of the 3 drill :rig :and 'thru rotary .drilling .-table 30. .A circulating swivel 32 -on--the upper endtofithelkelly makes a connection with a flexible conduit or. hose 34 for delivery of drilling fluid from:standpip e.36, usually extending vfrom the floor oftherig. x-Flexible conduit 3.4 is provided .solas to allow freedom1of-movement of=kelly-':24.as the drilling; progresses and joints areadded; to 'thedrill'string. .The :swivel is supported 'bY hOOk SS .which, .in .turn, is supported from the-crown block 1 by :conventional' means (not shown).

.Drilling mud flowingzfrom the upperendof the casing ,thru line '26; passesiinto a' first compartment 40 of'a'mud boxs42 which is closed except;-for.a..vent'line .44 and the mud seal outlet 46. at the bottom. :A second; compartment :48 .is open -atthe top ,and discharges over shale shaker 50. Flow'of mud as indicated by dotted line 52 -is into mud tank;5 4.

Mud is'circulated intostandpipe 36 by means of mud p mp .56, po io d. conduitfifl whhhconn d re y w t alo e ec qn e zmu tt nkei an h hel ,end ofstandpipe-36.

The aeration apparatus or equip1 nent 2 comprises a conventional air, compressor 60 which. hasan outlet line 62 leading intoa surge tank;64. ,An airline 66 connects surge tank 64 with standpipe 36. Positioned in air line is ameter-ingd vic s, a ta -amine -69. co a n n a vblee v .0, an gra n Q .9 v ve 72 n 74- ,Als i ude i .t ait line i a n-9 h c va 76 l 7 8 f pr vent n bac .fi 10 fl i ,f qm,-, an pipe 3 6.towardeompressonfifl Qheck valve 7 8 is .a rap d-.a ngwch k v l e-a dtun tiqn t p v n fi o zrm dv into. th line ups r am th e whi ch valve is o .sl e ac desig an ..fun ion .P i cipally as .a safety. .devicelwhich functions whenfvalve 'l s fails. .A pressure-record er 80. indicates thepressure in line.,.66. A conventional ,cornpressoncontrol means 8.2,;cont'ro st e. operation-Letiti compr s asrwu ed in aerated drilling mud drilling operation.

Shown in. the hollow drill string are a first check valve 84 and a second check valve 86' between couplings 88. Check valve 84 is inserted, preferably at the first or second joint in the drill string below kelly 24, when operating with aerated drilling mud. As hole is made and additional pipe joints are connected to the upper end of the drill string in conventional manner, check valve 84 correspondingly progresses downthe bore hole and func tions when uncoupling the .kelly from the upper end of the drillstring to preventself-unloading of the aerated mud ontothe drilling-rig platform. As additional hole is made and after several pipe joints have been added above check valve:84, it is desirable, in the event that the drill bit is still functioning satisfactorily, to incorporate a second check valve 86 in the drill string when a joint of pipe is being added. Check valves 84 and 86 may be of the same or different construction and of any suitable construction which permits circulation .of mud downwardly in the drill string .but closes when the mud tends to flowupwardly, thereby shutting off the flow of fluid therethru. Plain flapper, .ventedflapper, and spring ball types of float or check ;valves are commercially available and function satisfactorily in the operation of the invention. While two checkvalves-are shown more than two may be used to advantage whendrillinga consider- ;able depth with the same bit, the number depending on the amount of hole made.

Figure 2 shows-a two-cone bit ofconventional design comprising ;a body :section :90 and a threaded shank section 92 which screwsinto the end of drill collar 94.

A tricone bit may be utilizedin .lieu of the two-cone bit. The shank of the drill bit providesa fluid passageay 9 wh ch. leads a orco d t zi h in turn, .Pw

vide -a fluid passageway toreach of the cones of the drill thereby permitting circulation of drilling fluid from cqndu 0, n th dri st in nto the bore h and the annulus between the drill string and the casing .or

.lgelly isremoved forthis purpose; or for the purpose of adding a pipe joint; and theball iscirculated to the drill bit along with the drillingfluidwhere it is readily seated in one of theconduits extending thruthe drill bit, as shown.

In operationwith aerated drilling fluid, it is desirable to replace the aerated fluid by circulating non-aerated fluid to-fill up the drillvstring and annulus surrounding same before pulling the string (for bit replacement, etc.); otherwise, the aeratedmud in the hole will unload as pressure is released and expansion of the airlin the fluid takes place. Then whenthe string isrerunaerated fluid is circulated to displace the non-aerated heavy fluid. In such operation the ballplug vin the bit is not placed in the new bit (or replaced old bit in the event the bit is not changed);in order to facilitate theflow of fluid thru the bit until the heavy non-aeratedfluid is displaced. At about this time a ball or similar plug is again inserted in the aerated drilling fluid at the upper .end of thestring and is circulated to the bit where it seats in oneof the conduits thereinso as to again adapt the flow to the lighter drilling fluid.

It isalso feasible to circulate non-aerated drilling fluid .down at least to, the levelof the upperrnost check valve before opening the upper end of. the dn'll string to th tmosp r t dd p p o ts .th y avoiding unloadingof aerated fluidabove thelcheclc valve.

C t i m d atiqnsg th vent wil b s me p n t t o sk l ed in th a t. a t .il l iret t lfi tails disclosed are not to be construedas imposingunnecessary limitations on the invention.

I claim:

l Drilling apparatus for use with drilling fluid containing compressed gas in gaseous phase comprising a hollow imperforate drill string; a bit on the bottom end of said string having at least one conduit therethru connected with said hollow drill string; a kelly on the upper end of said string; and a first upwardly-closing check valve in an upper section of said string a substantial distance below said kelly, and a second upwardlyclosing check valve in an upper section of said string between said kelly and said first check valve said second valve being adapted to pass liquid downwardly thru the drill string from the upper end thereof and to close when said kelly is removed and gas in said fluid between said first and second check valves expands, and conduit means connecting the upper end of said kelly with a source of aerated liquid drilling fluid.

2. A process for drilling a well with a rotary drilling means comprising rotating a hollow drilling means having a kelly on the upper end and a cutting means on the lower end thereof in a bore hole so as to bore into an earth formation; circulating an aerated drilling liquid downwardly thru said drilling means from the upper end thereof thru said cutting means and upwardly thru an annulus between said drilling means and the wall of said bore hole; running a back flow prevention means in an upper section of said drilling means and, as hole is made, adding further sections of hollow drilling means intermediate said kelly and said back flow prevention device, whereby said back flow prevention device prevents backflow of aerated fluid from the drilling means below; continuing drilling until replacement of said cutting means is desired; pulling said drilling means and replacing said cutting means; rerunning the said hollow drilling means and, as drilling means is rerun, inserting said back flow prevention means therein at a position in'said drilling means closer to said kelly than it was just before pulling; and continuing the drilling.

3. The process of claim 2 wherein said drilling fluid comprises a drilling mud.

4. The process of claim 2 including the insertion of a second back flow prevention device in said drilling means at a point above first said back flow prevention device to avoid overflow of the aerated drilling fluid from me drilling means above first said back flow prevention device when said kelly is removed to insert an additional section of hollow drilling means.

5. The process of claim 4 wherein said fluid is a drilling mud.

6. In a process for drilling a well with a rotary drilling means comprising a hollow drilling means containing a terminal rotary cutting means having a plurality of passages therein for flow of drilling mud from the drilling means thru the cutting means, wherein, after a portion of the hole is drilled, a change from a non-aerated drilling mud to an aerated drilling mud of lower viscosity is made, the steps comprising inserting in the mud in said string a medium adapted to plug one of said passages and circulating same to the cutting means so as to plug one of said passages and thereby adapt the cutting means to more desirable flow conditions for said acrated mud and flowing said aerated mud thru the cutting means via at least one of said plurality of passages.

7. A process for drilling a well with a rotary drilling means comprising rotating a hollow drilling means having a kelly on the upper end and a cutting means on the lower end thereof in a bore hole so as to bore into an earth formation; circulating an aerated drilling liquid downwardly thru said drilling means from the upper end thereof thru said cutting means and upwardly thru an annulus between said drilling means and the wall of said bore hole; running a first back flow prevention means in an upper section of said drilling means and, as hole is made, adding sections of hollow drilling means to said drilling means intermediate said kelly and said first back flow prevention means, thus causing said first back flow prevention device to move a substantial distance down the hole; thereafter adding at least a second back flow prevention means in an upper section of said drilling means above said first back flow prevention means, whereby said second back flow prevention means prevents backflow of aerated fluid from the sections of hollow drilling means between said first and second back flow prevention means because of expansion of gas in said aerated drilling liquid.

8. A well-drilling process comprising drilling a bore hole with rotary drilling means comprising a hollow drilling means containing a terminal rotary cutting means having a plurality of passages therein for flow of drilling mud from the drill string into the bore hole which comprises drilling in an earth formation with an aerated drilling mud and with one of said conduits closed until pulling of said cutting means is desired; thereafter circulating non-aerated drilling mud thru said drilling means and the annulus surrounding same so as to displace said aerated mud; pulling said drilling means and replacing said cutting means with a similar cutting means having all conduits therein open; rerunning said drilling means and circulating aerated drilling mud thru said drilling means and into the surrounding annulus and thus displacing the non-aerated mud; inserting in the mud in said drilling means a medium adapted to plug one of said passages; and circulating said aerated mud until said medium plugs one of said passages, while leaving at least one other of said passages open.

References Cited in the file of this patent UNITED STATES PATENTS 1,681,502 Sheldon Aug. 21, 1928 1,867,832 Hill July 19, 1932 2,092,822 West Sept. 14, 1937 2,132,161 Hall Oct. 4, 1938 2,169,675 Bays Aug. 15, 1939 2,238,895 Gage Apr. 22, 1941 2,595,715 Sloan May 6, 1952 

